This invention relates to a glass melting furnace and to a method for melting glass therein. More particularly, it relates to a glass melting furnace having a melting section and an adjacent refining section which are interconnected via a cross-section reducing step or barrier.
In conventional horizontal glass melting furnaces, glass is melted and subsequently refined in adjacent refining and melting sections. Auxiliary heating electrodes can be provided in furnaces of this type. But furnace efficiency is unsatisfactory and the quality of the molten glass produced at high throughout rates is generally not satisfactory. In particular, large horizontal furnaces having large molten bath surface areas are low in efficiency compared to their volumes.
The horizontal flow that takes place in such glass melting furnaces can be controlled only with difficulty, and in practice some portions of the molten glass enter the passage connecting the melting and refining sections after an extremely short dwell period in the melting trough which seriously limits the performance of such troughs because with such a short dwell period, the molten glass still includes bubbles.
In vertically operated, electric glass melting furnaces, the electrodes are arranged in a plurality of vertically spaced planes (of U.S. Pat. No. 3,742,111 issued Jan. 26, 1973). Vertical furnaces, however, are of special construction, and it is not possible to convert conventionally heated horizontal furnaces into vertical electric furnaces.
Furthermore, vertical furnaces are operated solely with electric energy, are fully dependent on the supply of electrical energy, and the use of less expensive fuels such as gas or oil is not possible.
The present invention provides a method for melting glass and a glass melting furnace which do not suffer from the above discussed disadvantages. According to the present invention, it is now possible to melt glass with high quality by using a combination of conventional flame heating and electric energy. The furnace thus has high efficiency based on its volume. In particular, the method of the invention allows the conversion of existing, conventionally heated glass melting furnaces in such a manner that they operate with a high proportion of electric energy to produce improved quality glass with a substantial increase in performance or capacity. In addition, according to the invention, furnaces can be operated with conventional heating alone or with electric heating alone.
On a whole, the production of high quality glass is rendered more economical according to the invention because, depending on the cost of the different sources of heating energy, the energy proportions may be suitably selected, and additionally, the construction of furnaces according to the invention, by converting existing furnaces, is particularly economical, quick and easy.